Current production automobiles include a body formed of a plurality of longitudinal structural members. In a front engine automobile of this type, a frontal impact has three principle paths for impact force transmission to and through the vehicle's structure—two outer paths including upper and lower longitudinal frame members and a central path including the engine, transmission and possibly the engine cradle.
In a frontal impact at sufficiently high speeds, all three load paths are functional to absorb and dissipate the vehicle's energy as it rapidly decelerates. Testing has shown that the outer load paths together dissipate 40% to 70% of the vehicle's energy, while the central path dissipates the remainder. The longitudinal frame members are designed to include crush zones to dissipate energy by deforming at force levels that will provide passenger compartment decelerations consistent with occupant safety requirements.
Crush zones are typically designed into vehicle structures by including geometric features that localize deformation such as thinner cross sections or depressions/indentations in the structure. Another method contemplates incorporating different materials with better crush performance into the vehicle structure to form a “crush box” which provides the desired energy dissipation function. However, each of these techniques require an adaptation of the vehicle structure which may compromise the structural stiffness, as well as increase the cost and complexity of the vehicle's structure. Thus, there is a need for technology to introduce a crush zone into a vehicle structure without significantly impacting the structural stiffness, cost and complexity of the vehicle structure.